1. Field of the Invention
The present invention is directed toward the field of receivers, and more particularly toward integrating an entire receiver on a monolithic integrated circuit.
2. Art Background
In general, televisions include circuits to demodulate radio frequency television signals to generate video and sound signals. The video and sound signals provide the information necessary to form the television picture and sound, respectively. An ultrahigh frequency (“UHF”)/very high frequency (“VHF”) tuner is one type of circuit found in television receivers. In general, the UHF/VHF tuner receives a radio frequency (“RF”) television signal that includes a plurality of channels. The channels are modulated on a carrier frequency. The carrier frequency may be in the UHF spectrum or the VHF spectrum. The television is set or tuned to receive a specific channel (e.g., channel 2). The U/V tuner processes the RF television signal based on the channel selected, and generates an intermediate frequency (“IF”) signal. In the United States, the intermediate frequency, used in television receivers, is set to a frequency of 45.75 Mhz.
Television receivers also include circuits to perform intermediate frequency processing. These IF television circuits typically employ surface acoustic wave (“SAW”) filters. The SAW filter conditions the IF signal prior to demodulation (i.e., prior to extracting the video and audio signals). The SAW filter rejects or suppresses the energy bands associated with channels adjacent to the desired channel (i.e., the selected channel). To this end, the SAW filter provides a Nyquist slope bandpass response for the IF signal.
Typically, Federal Communications Commission regulations mandate receivers operate at higher intermediate frequencies to reduce EMI emissions from the device. Because of this, prior art television receivers operate at intermediate frequencies of 45.75 MHz. The processing of intermediate frequencies at 45.75 MHz mandates use of an external surface acoustic wave (“SAW”) filter (i.e., external to the television tuner integrated circuit). If an external SAW filter is used, radiation emanates from the electrical conductors that couple the integrated circuit tuner to the external SAW filter. Because of this emission of radiation, the receiver must comply with the FCC regulation, and the receiver must process the signals at an intermediate frequency of 45.75 MHz.
It is desirable to develop a television receiver that does not require an external SAW filter. It is also desirable to develop a television receiver implemented on a single integrated circuit chip.